[FileCheck] Report missing prefixes when more than one is provided.

If more than a prefix is provided - e.g. --check-prefixes=CHECK,FOO - we
don't report if (say) FOO is never used. This may lead to a gap in our
test coverage.

This patch introduces a new option, --allow-unused-prefixes. It
currently is set to true, keeping today's behavior. After we explicitly
set it in tests where this behavior was actually intentional, we will
switch it to false by default.

Differential Revision: https://reviews.llvm.org/D90281

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/utils/FileCheck/FileCheck.cpp b/llvm/utils/FileCheck/FileCheck.cpp
index b48ae0b..1721b23 100644
--- a/llvm/utils/FileCheck/FileCheck.cpp
+++ b/llvm/utils/FileCheck/FileCheck.cpp
@@ -77,6 +77,10 @@ static cl::opt<bool> AllowEmptyInput(
     cl::desc("Allow the input file to be empty. This is useful when making\n"
              "checks that some error message does not occur, for example."));
 
+static cl::opt<bool> AllowUnusedPrefixes(
+    "allow-unused-prefixes", cl::init(true),
+    cl::desc("Allow prefixes to be specified but not appear in the test."));
+
 static cl::opt<bool> MatchFullLines(
     "match-full-lines", cl::init(false),
     cl::desc("Require all positive matches to cover an entire input line.\n"
@@ -771,6 +775,7 @@ int main(int argc, char **argv) {
     return 2;
 
   Req.AllowEmptyInput = AllowEmptyInput;
+  Req.AllowUnusedPrefixes = AllowUnusedPrefixes;
   Req.EnableVarScope = EnableVarScope;
   Req.AllowDeprecatedDagOverlap = AllowDeprecatedDagOverlap;
   Req.Verbose = Verbose;